Geneva - The European Organization for Nuclear Research (CERN) officially inaugurated its experiment to probe the origins of the universe on Tuesday, even though a technical hitch last month shut it down within days of starting.

Amid massive security, top scientists and ministers went to CERN's sprawling site on the French-Swiss border to mark the start of the biggest scientific experiment ever launched, which will investigate the building blocks of matter to understand what makes the universe tick.

"The greatest philosophers, the greatest mystics, the greatest poets have never ceased meditating on these mysteries -- the mystery of matter and the mystery of the creation of the universe," French Prime Minister Francois Fillon said.

"These two intertwined questions have never stopped fascinating humanity," he told the inauguration ceremony.

The ceremony was held to thank the governments of CERN's 20 European member states and six collaborating nations from Russia to the United States for funding the $9 billion machine.

CERN's Large Hadron Collider, the biggest and most complex machine ever built, will study the smallest building blocks of matter, sub-atomic particles.

CERN scientists launched the experiment on September 10, firing beams of proton particles around the 27-km (17-mile) tunnel outside Geneva 100 meters (330 feet) underground.

But nine days later they had to shut it down because of a helium leak caused by a faulty electrical connection between two of the accelerator's huge magnets.

The experiment, which will run for 10-15 years, will not resume until spring 2009.

When it works again, the collider will recreate conditions just after the Big Bang believed by most cosmologists to be at the origin of our expanding universe 13.7 billion years ago.

It will send beams of sub-atomic particles around the tunnel to smash into each other at close to the speed of light.

These collisions will explode in a burst of intensely hot energy and of new and previously unseen particles.

CERN, which invented the Worldwide Web nearly 20 years ago, has set up a high-power computer network linking 7,000 scientists in 33 countries to crunch the data flow, enough to create a tower of CDs more than twice as high as Mount Everest.